You can add family members during your employer's open enrollment period. If it is outside the open enrollment period, you may only add family members under certain qualifying circumstances, such as marriage, birth, or adoption of a child, or if your spouse loses coverage through his or her employer or another plan. In cases like these, you are eligible for a special enrollment period to add a family member. If you want to enroll your family member in your employer plan, you have 30 days from the date of the triggering event to do so. (45 C.F.R. § 146.117).